Measuring instrument



E. H. BRISTOL.

MEASURING INSTRUMEM.

APPLICATION FILED JAN. I9. 1918.

1,340,148. Patented May18,1920.

UNITED STATES PATENT OFFICE.

EDGAR H. BRISTOL, OF FOXBORO, MASSACHUSETTS, ASSIGNOR TO THE FOXIBOROCOMPANY, OF FOXBORO, MASSACHUSETTS, A CORPORATION OF MASSACHU- SETTS.

MEASURING INSTRUMENT.

Specification of Letters Patent.

19, 1918. Serial No. 212,556.

To all whom it may concern Be it known that I, EDGAR H. BRISTOL, acitizen of the United States, and resident of Foxboro, in the county ofNorfolk and State of Massachusetts, have invented an Improvement inMeasuring Instruments, of which the following description, in connectionwith the accompanying drawings, is a specification, like characters onthe drawings representing like parts.

This application is a (livisionof my cop pnding application, Serial No.751,729, filed arch 3d, 1913.

This invention relates to mechanism for measuring the pressures offluids, especially gases.

My invention will best be understood by reference to the followingdescription taken in connection with the accompanying illustrativedrawing wherein I have shown a broken away section of a measuringinstrument embodying my invention.

In the drawing I have illustrated the invention as applied to arecording instrument having a dial 3 adapted to be rotated by suitableclockwork (not shown) in the case 5 and over which sweeps a hand or pen7 controlled by pressure responsive mechanism. Herein the hand is movedby a crank 9 from a shaft 11 connected by a spring device 13, such as isdescribed in my prior application, Serial Number 741,198, filed Jan. 10,1913, with a shaft 15 mounted in a tubular bearing 17 carried by a plug19 in the case 5. The bearing is laterally recessed at- 20 to permitattachment to the shaft of a link 21 secured to an expansion tube 23 ofwell-known form mounted in the pressure receiving chamber 25 which issecured to the back of case 5. In the embodi ment of the invention hereshown the tube responds to differential pressures and moves the hand 7in amount correspondin to the algebraic sum of the pressure wit in thechamber 25 but external to the tube 23, (such pressure being admittedthrough pipe 27,) and the pressure admitted to the interior of the tubethrough a port 29. Obviously one of the two pressures might be merelythe pressure of the atmosphere.

. To insure accuracy of the instrument there should be no leaking andthis in many instances is desirable for other reasons, as where thepressures the difference of which is to be measured are those of gaseswhich are noxious or even poisonous. My present mvention provldes for aneffective sealing of the chamber 25 insuring the accuracy of PatentedMay 18, 1920. Original application filed March 3, 1913, Serial No.751,729. Divided and this application filed January the instrument,protecting the parts thereof,

such as the clockwork mechanism, from contact with the fluid thepressure of which is measured, and preventing its escape into thesurrounding atmosphere in however small quantities. The means employed,more over, facilitate the registering action of the instrument.

Obv1ously one source of leakage is the space between shaft 15 and itsbearing 17 and since the shaft must turn freely and in response to veryslight forces, it is difiicult to pack this shaft. My present inventionprovides for a fluid seal which will prevent the escape of gas aroundthe shaft 15 to the exterior of the chamber 25 and which not only willnot impede but will facilitate the rotary movements of the shaft. Forthis purpose I provide on the exterior of the casing 5 a fluid reservoir31 adapted to be filled with oil of suitable viscosity. A discharge pipe33 leads from the bottom of this reservoir and leads through duct 35,through one or more discharge pipes 37 (herein two), to the bearing ofshaft 15. The pipes 37 may discharge to suitable bores 39 in the bearingabout the shaft, these bores in the present instance being at opposite.the shaft of the link 21.

To facilitate feeding of the oil from the reservoir to the shaft againstthe pressure of fluid in the chamber 25 and for further purposeshereinafter'to be mentioned, the interior of the chamber is connected bya port 41 and a pipe 43 to the top of the reservoir 31, so that thepressure on the surface of the oil is the same as the pressure withinthe chamber 25.

The mechanism just described not only insures thorough lubrication ofthe shaft in the ordinary way but has a particular function in aninstrument of this kind. The oil around the shaft forms a fluid seal forthe same which prevents the escape of gas from the chamber25. Thepressure of the gas, however, is such that the oil is slowly forced tothe left .in the figure and gradually seeps out from the left-hand endof the bearing 17. If the shaft were oiled in the ordinary way it wouldsoon become dry and hard to age caused by seepage.

, the-oil"which is driven down by the gas pressure communicated to itssurface by the pipe 43. Hence, the bearing is always lubricatedand isefiiciently sealed, the leakage or seepage being from the reservoir 31to the left-hand of the bearing and not from the chamber 25 to that endof the bearing.

Preferably a tube 45 is provided which leads to the exterior of thechamber 25 and serves to maintain the inner end of shaft 15 underexterior pressure. Thus not only are the end pressures on the shaftbalanced but effective lubrication. of the right hand end of bearing l7is p'rovide'd for in the manner already explained.

The reservoir 31 is of such size as to require only infrequent filling.I may, however, provide small valves 4C7 and 49 in the pipes 33 and 43respectively, so that the flow of oil from the reservoir may be cut offand the pressure from the interior of the chamber 25 excluded when it isdesired to open the reservoir for refilling.

1 Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is 1. In a device of the class described, thecombination of an index; responsive means for controlling the same; achamber containing said responsive means; means for transmittingmovement from said res onsive means to said index including an e ongatedshaft and bearing; connections from said responsive means to said shaft;oil supply means opening to the exterior of said chamber arranged tosupply oil to said shaft at points on opposite sides of the point ofconnection of said connections with said shaft; and means formaintaining the same pressures in said chamber and in said oil supplymeans.

2. In a device of the class described, the.

combination of an ,index; responsive means; a chamber containing thelatter; means to conduct pressures to, said responsive means andchamber; means to transmit movement of said responsive means to saidindex in.- cluding a shaft and its bearing, the latter having a lateralrecess therein; means connecting said responsive means to said shaftthrough said recess; lubricant sup ly means accesslble from the exteriorof said chamber arranged to supply lubricant to said shaft at oppositesides of said recess; and means to maintain the same pressures in saidchamber and in said lubricant supply means.

3, In a device of the class described, the combination of an index;responsive means; a chamber inclosing the latter; means to conduct fluidpressures to said responsive means and chamber; means for transmittingmovement from said responsive means to said index including a shaft andbearing projecting from the interior of said chamber to the exteriorthereof; means to connect said responsive means to said shaft; a closedoil reservoir arranged to supply oil to said shaft at points on oppositesides of the point of connection with said shaft;

and means for maintaining the pressure of said chamber in saidreservoir.

4:. In a device of the class described, the combination of an index;responsive means; a chamber inclosing the latter; means to conduct fluidpressures to said responsive means and chamber; means to transmitmovement of said responsive means to said lndex including a shaft andits bearing;

connecting means from said responsive means to said shaft and connectedto the shaft between the ends of the shaft bearing; a reservoir;conduits leading from sald reservoir to points of said bearing oppositethe point of connection of said connecting means; and a conduit leadingfrom said chamber to the top of said reservoir whereby to maintain thepressure in said chamber on the surface of the oil in said reservoir.

5. In a device of the class described, responsive means; a chambercontaining the latter; means to conduct pressures to said responsivemeans and chamber; an index exterior to the chamber; means to transmitmovement of said responsive means to said index including an elongatedbearing, a shaft therein extending through the wall of the chamber, aconnection between the shaft and the responsive means, said bearingbeing laterally recessed to provide for such con- 1 nection; a closedlubricant reservoir; a duct therefrom opening to? said shaft on oppositesides of the recess a connection between the interior'of the reservoirand the chamber and a connection 45-from the rear of EDGAR H. BRISTOL.

